This invention relates to a method for the formation on the surface of a sintered silicon nitride type ceramic article a coating of a compound containing titanium or zirconium.
Compounds containing titanium or zirconium such as, for example, titanium nitride and titanium carbide excel in heat resistance and resistance to wear. Thus, coatings of such compounds applied mainly to metallic members are used as cutting tools and other similar tools.
In recent years, attempts have been made at conferring improved properties upon existing sintered silicon nitride ceramic articles useful as heat-resisting structural materials and wear-resistant materials by applying coatings of such compounds thereon or, by utilizing the fact that such coatings are formable in electroconductive composition, at developing a method of joining sintered ceramic articles with metallic members and consequently widening the range of applications found for sintered ceramic articles.
Physical vapor deposition (PVD), chemical vapor deposition (CVD), flame spraying, etc. are possible methods for forming coatings of metal compounds on inorganic substrates such as sintered ceramic articles. All these methods, however, invariably require materials under treatment to be placed in special chambers and subjected to a coating operation with the degree of vacuum inside the chambers controlled very rigidly. Thus, they have the disadvantage that they find mass treatment hardly feasible, impose limits on dimensions of materials to be treated, and suffer from high cost of operation.